代码无法执行，提示Run Tasks错误

package com.example.data_sqlite;

import android.Manifest;
import android.content.pm.PackageManager;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Environment;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v4.widget.CursorAdapter;
import android.support.v4.widget.SimpleCursorAdapter;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.Toast;

import java.util.List;

public class MainActivity extends AppCompatActivity {
    private static final String TAG = "MainActivity";
    private EditText main_name,main_age,main_id;
    private RadioGroup main_genderGroup;
    private RadioButton main_genderGroup_boy,main_genderGroup_girl;
    private String genderStr="男";
    private SQLiteDatabase db;
    private ListView main_listview;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState)6
        setContentView(R.layout.activity_main);

        //6.0以上需要设置动态权限
        requestAllPower();
        //初始化view
        initview();
        //初始化db
        initDB();


    }



    private void initview() {
        main_name = (EditText)findViewById(R.id.main_name);
        main_age = (EditText)findViewById(R.id.main_age);
        main_id= (EditText) findViewById(R.id.main_id);
        main_listview = (ListView)findViewById(R.id.main_listview);

        main_genderGroup = (RadioGroup)findViewById(R.id.main_genderGroup);
        main_genderGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup radioGroup, int i) {
                if(i==R.id.main_genderGroup_boy){
                    genderStr =  "男";
                }else
                {
                    genderStr =  "女";
                }
            }
        });
    }

    public void operate(View v){
        switch (v.getId()){
            case R.id.main_btn_insert:
                insertsqlite();
                break;
            case R.id.main_btn_select:
                selectsqlite();
                break;
            case R.id.main_btn_update:
                break;
            case R.id.main_btn_del:
                break;
        }
    }

    private void selectsqlite() {
        String sql2 = "select * from info_stu ";
        String idstr = main_id.getText().toString();
        if(!idstr.equals("")){
            sql2 = "select * from info_stu where _id = "+idstr;
        }
        Log.e(TAG, "selectsqlite: "+sql2 );

        Cursor c = db.rawQuery(sql2,null);

        SimpleCursorAdapter adapter = new SimpleCursorAdapter(
                MainActivity.this,
                R.layout.activity_main_item,
                c,
                new String[]{"_id","name","age","gender"},//数据表头
                new int[]{R.id.main_listview_id,R.id.main_listview_name,R.id.main_listview_age,R.id.main_listview_gender}, //对应的页面显示ID
                CursorAdapter.FLAG_REGISTER_CONTENT_OBSERVER //当数据发生变化时，当前数据同步变化；
                );
        main_listview.setAdapter(adapter);

    }

    private void insertsqlite() {

        String sql = "insert into info_stu(name,age,gender) values(?,?,?)";
        String main_nameStr = main_name.getText().toString();
        String main_ageStr = main_age.getText().toString();
        //String main_idStr = main_id.getText().toString();
        db.execSQL(sql,new String[]{main_nameStr,main_ageStr,genderStr});

    }

    public void requestAllPower() {
        if (ContextCompat.checkSelfPermission(this,
                Manifest.permission.WRITE_EXTERNAL_STORAGE)
                != PackageManager.PERMISSION_GRANTED) {
            if (ActivityCompat.shouldShowRequestPermissionRationale(this,
                    Manifest.permission.WRITE_EXTERNAL_STORAGE)) {
            } else {
                ActivityCompat.requestPermissions(this,
                        new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE,
                                Manifest.permission.READ_EXTERNAL_STORAGE}, 1);
            }
        }
    }

    private void initDB() {
        //如果只有一个路径则数据库放入私有目录
        //如果带SDK目录，则数据库在指定的路径下，
        String path = Environment.getExternalStorageDirectory()+"/student.db";
        SQLiteOpenHelper helper = new SQLiteOpenHelper(this,path,null,2) {
            @Override
            public void onCreate(SQLiteDatabase sqLiteDatabase) {
                Toast.makeText(MainActivity.this,"数据创建",Toast.LENGTH_SHORT).show();
                sqLiteDatabase.execSQL("CREATE TABLE `info_stu` ( " +
                        " `_id` INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, " +
                        " `name` varchar(30), " +
                        " `age` INTEGER ," +
                        " `gender` Ivarchar(30) " +
                        ");");
            }

            @Override
            public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
                Toast.makeText(MainActivity.this,"数据升级",Toast.LENGTH_SHORT).show();
            }
        };
        //获取数据库对象
        //数据库存在，直接打开，不存在则创建然后打开；
        db = helper.getReadableDatabase();
    }

}

老师，我的代码出现如下问题：无法通过编译，

操作步骤：

一开始没有任何问题，逐渐在执行过程中发现，执行后红色的执行停止按钮变灰色；
但是点击绿色三角执行按钮依然可以强制重新执行；
经过多次反复直接绿色三角执行后，出现无法编译错误；

猜测并尝试解决：

1. Build -> Clean Project ; Build -> Rebuild Project 无效

2. 关闭模拟器，重新启动无效；

org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':data_sqlite:compileDebugJavaWithJavac'.

at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:100)

at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:70)

at org.gradle.api.internal.tasks.execution.OutputDirectoryCreatingTaskExecuter.execute(OutputDirectoryCreatingTaskExecuter.java:51)

at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:62)

at org.gradle.api.internal.tasks.execution.ResolveTaskOutputCachingStateExecuter.execute(ResolveTaskOutputCachingStateExecuter.java:54)

at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:60)

at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:97)

at org.gradle.api.internal.tasks.execution.CleanupStaleOutputsExecuter.execute(CleanupStaleOutputsExecuter.java:87)

at org.gradle.api.internal.tasks.execution.ResolveTaskArtifactStateTaskExecuter.execute(ResolveTaskArtifactStateTaskExecuter.java:52)

at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:52)

at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:54)

at org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:43)

at org.gradle.api.internal.tasks.execution.CatchExceptionTaskExecuter.execute(CatchExceptionTaskExecuter.java:34)

at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker$1.run(DefaultTaskGraphExecuter.java:248)

at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:336)

at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:328)

at org.gradle.internal.progress.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:199)

at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:110)

at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:241)

at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:230)

at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker.processTask(DefaultTaskPlanExecutor.java:123)

at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker.access$200(DefaultTaskPlanExecutor.java:79)

at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker$1.execute(DefaultTaskPlanExecutor.java:104)

at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker$1.execute(DefaultTaskPlanExecutor.java:98)

at org.gradle.execution.taskgraph.DefaultTaskExecutionPlan.execute(DefaultTaskExecutionPlan.java:626)

at org.gradle.execution.taskgraph.DefaultTaskExecutionPlan.executeWithTask(DefaultTaskExecutionPlan.java:581)

at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$TaskExecutorWorker.run(DefaultTaskPlanExecutor.java:98)

at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor.process(DefaultTaskPlanExecutor.java:59)

at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter.execute(DefaultTaskGraphExecuter.java:128)

at org.gradle.execution.SelectedTaskExecutionAction.execute(SelectedTaskExecutionAction.java:37)

at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:37)

at org.gradle.execution.DefaultBuildExecuter.access$000(DefaultBuildExecuter.java:23)

at org.gradle.execution.DefaultBuildExecuter$1.proceed(DefaultBuildExecuter.java:43)

at org.gradle.execution.DryRunBuildExecutionAction.execute(DryRunBuildExecutionAction.java:46)

at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:37)

at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:30)

at org.gradle.initialization.DefaultGradleLauncher$ExecuteTasks.run(DefaultGradleLauncher.java:314)

at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:336)

at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:328)

at org.gradle.internal.progress.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:199)

at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:110)

at org.gradle.initialization.DefaultGradleLauncher.runTasks(DefaultGradleLauncher.java:204)

at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:134)

at org.gradle.initialization.DefaultGradleLauncher.executeTasks(DefaultGradleLauncher.java:109)

at org.gradle.internal.invocation.GradleBuildController$1.call(GradleBuildController.java:78)

at org.gradle.internal.invocation.GradleBuildController$1.call(GradleBuildController.java:75)

at org.gradle.internal.work.DefaultWorkerLeaseService.withLocks(DefaultWorkerLeaseService.java:152)

at org.gradle.internal.invocation.GradleBuildController.doBuild(GradleBuildController.java:100)

at org.gradle.internal.invocation.GradleBuildController.run(GradleBuildController.java:75)

at org.gradle.tooling.internal.provider.runner.ClientProvidedBuildActionRunner.run(ClientProvidedBuildActionRunner.java:62)

at org.gradle.launcher.exec.ChainingBuildActionRunner.run(ChainingBuildActionRunner.java:35)

at org.gradle.tooling.internal.provider.ValidatingBuildActionRunner.run(ValidatingBuildActionRunner.java:32)

at org.gradle.launcher.exec.RunAsBuildOperationBuildActionRunner$1.run(RunAsBuildOperationBuildActionRunner.java:43)

at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:336)

at org.gradle.internal.progress.DefaultBuildOperationExecutor$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutor.java:328)

at org.gradle.internal.progress.DefaultBuildOperationExecutor.execute(DefaultBuildOperationExecutor.java:199)

at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:110)

at org.gradle.launcher.exec.RunAsBuildOperationBuildActionRunner.run(RunAsBuildOperationBuildActionRunner.java:40)

at org.gradle.tooling.internal.provider.SubscribableBuildActionRunner.run(SubscribableBuildActionRunner.java:51)

at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:47)

at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:30)

at org.gradle.launcher.exec.BuildTreeScopeBuildActionExecuter.execute(BuildTreeScopeBuildActionExecuter.java:39)

at org.gradle.launcher.exec.BuildTreeScopeBuildActionExecuter.execute(BuildTreeScopeBuildActionExecuter.java:25)

at org.gradle.tooling.internal.provider.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:80)

at org.gradle.tooling.internal.provider.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:53)

at org.gradle.tooling.internal.provider.ServicesSetupBuildActionExecuter.execute(ServicesSetupBuildActionExecuter.java:57)

at org.gradle.tooling.internal.provider.ServicesSetupBuildActionExecuter.execute(ServicesSetupBuildActionExecuter.java:32)

at org.gradle.tooling.internal.provider.GradleThreadBuildActionExecuter.execute(GradleThreadBuildActionExecuter.java:36)

at org.gradle.tooling.internal.provider.GradleThreadBuildActionExecuter.execute(GradleThreadBuildActionExecuter.java:25)

at org.gradle.tooling.internal.provider.ParallelismConfigurationBuildActionExecuter.execute(ParallelismConfigurationBuildActionExecuter.java:43)

at org.gradle.tooling.internal.provider.ParallelismConfigurationBuildActionExecuter.execute(ParallelismConfigurationBuildActionExecuter.java:29)

at org.gradle.tooling.internal.provider.StartParamsValidatingActionExecuter.execute(StartParamsValidatingActionExecuter.java:69)

at org.gradle.tooling.internal.provider.StartParamsValidatingActionExecuter.execute(StartParamsValidatingActionExecuter.java:30)

at org.gradle.tooling.internal.provider.SessionFailureReportingActionExecuter.execute(SessionFailureReportingActionExecuter.java:59)

at org.gradle.tooling.internal.provider.SessionFailureReportingActionExecuter.execute(SessionFailureReportingActionExecuter.java:44)

at org.gradle.tooling.internal.provider.SetupLoggingActionExecuter.execute(SetupLoggingActionExecuter.java:45)

at org.gradle.tooling.internal.provider.SetupLoggingActionExecuter.execute(SetupLoggingActionExecuter.java:30)

at org.gradle.launcher.daemon.server.exec.ExecuteBuild.doBuild(ExecuteBuild.java:67)

at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)